@mixin size($width, $height) {
    width: $width;
    height: $height;
}

@mixin square($size) {
    @include size($size, $size);
}

@mixin size-rem($width, $height) {
    @include size(rem($width), rem($height))
}

@mixin square-rem($size) {
    @include size-rem($size, $size);
}